Heat induced by electromagnetic absorption affects optical properties and experimental conditions. For this reason, thermal effects in optics remain important. In this work, we investigate thermal properties of a wire-grid polarizer (WGP). A WGP is a well-known optical polarizing device and easy to combine with planar structures such as microfluidic channel and other optical components. We analyzed thermal characteristics of a WGP by considering the effects of various geometric parameters: wire-grid period, height, and fill factor. For far-field calculation of optical characteristics, rigorous-coupled wave analysis (RCWA) has been used with 40 spatial harmonics. Together, we solved wave-coupled heat transfer equation by 2D finite element method (FEM) for computing electromagnetic-thermal characteristics. 2D FEM calculation was verified with RCWA and 3D FEM. From the analysis, it was shown that a fill factor was the most dominant geometrical parameter for near-field thermal extinction. In addition, TM polarized light has higher local temperature Tmax = 354.5 K than that of TE polarized light Tmax = 331.7 K with an incident power at 0.1 mW/μm2. Polarization switching was found to induce thermal extinction of 4.78 dB with a temperature difference ▵T = 54.3 K in an identical WGP structure. Furthermore, the ratio of steady-state time was almost uniform within 15%, because the heat transfer mechanism is almost identical for TE and TM polarization. Time scale was on the order of μs. We expect this result to be useful for the integration of WGPs in polarization-sensitive thermal switching applications.